Persons with physical impairments may find it difficult to open and close the door in various environments, such as, of example, the door to a courtroom witness box. Thus, people often depend on mechanical actuators to open and close doors. For such situations, a door having actuatable components that may be controlled from inside or outside of the witness box can assist a person entering or exiting the witness box.
The actuatable components of a witness box door must meet certain force requirements defined in the ANSI Code. Door actuators typically incorporate an override assembly having a control system that utilizes contact switches to sense obstructions encountered by the door components. Upon sensing an obstruction, the control system typically either shuts down the actuator, effectively stopping the components, or limits the force of the actuator by a current limit or pressure regulator. The override assembly may be either active or passive. An active override assembly uses powered controls to achieve force limits, and a passive type uses regulators to limit forces (such as hydraulic relief valves). An active assembly does not easily allow manual override, and passive systems can overheat.
It is desired to have a reliable override assembly that limits the force an actuator imposes on the actuatable components of the door without damaging the obstruction or the door components.